use std::cell::UnsafeCell;
use std::hash::{Hash, Hasher};
use std::os::raw::{c_int, c_void};
use std::rc::Rc;
use std::sync::atomic::{AtomicI32, Ordering};
use std::sync::Arc;
use std::{fmt, mem, ptr};

use parking_lot::Mutex;

use crate::error::Result;
#[cfg(not(feature = "luau"))]
use crate::hook::Debug;
use crate::state::{ExtraData, Lua, RawLua, WeakLua};

#[cfg(feature = "async")]
use {crate::value::MultiValue, futures_util::future::LocalBoxFuture};

#[cfg(all(feature = "luau", feature = "serialize"))]
use serde::ser::{Serialize, SerializeTupleStruct, Serializer};

// Re-export mutex wrappers
pub use app_data::{AppData, AppDataRef, AppDataRefMut};
pub(crate) use sync::{ArcReentrantMutexGuard, ReentrantMutex, ReentrantMutexGuard, XRc, XWeak};

/// Type of Lua integer numbers.
pub type Integer = ffi::lua_Integer;
/// Type of Lua floating point numbers.
pub type Number = ffi::lua_Number;

// Represents different subtypes wrapped to AnyUserData
#[derive(Debug, Copy, Clone, Eq, PartialEq)]
pub(crate) enum SubtypeId {
    None,
    #[cfg(feature = "luau")]
    Buffer,
    #[cfg(feature = "luajit")]
    CData,
}

/// A "light" userdata value. Equivalent to an unmanaged raw pointer.
#[derive(Debug, Copy, Clone, Eq, PartialEq)]
pub struct LightUserData(pub *mut c_void);

pub(crate) type Callback<'a> = Box<dyn Fn(&'a RawLua, c_int) -> Result<c_int> + 'static>;

pub(crate) struct Upvalue<T> {
    pub(crate) data: T,
    pub(crate) extra: XRc<UnsafeCell<ExtraData>>,
}

pub(crate) type CallbackUpvalue = Upvalue<Callback<'static>>;

#[cfg(feature = "async")]
pub(crate) type AsyncCallback<'a> =
    Box<dyn Fn(&'a RawLua, MultiValue) -> LocalBoxFuture<'a, Result<c_int>> + 'static>;

#[cfg(feature = "async")]
pub(crate) type AsyncCallbackUpvalue = Upvalue<AsyncCallback<'static>>;

#[cfg(feature = "async")]
pub(crate) type AsyncPollUpvalue = Upvalue<LocalBoxFuture<'static, Result<c_int>>>;

/// Type to set next Luau VM action after executing interrupt function.
#[cfg(any(feature = "luau", doc))]
#[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
pub enum VmState {
    Continue,
    Yield,
}

#[cfg(all(feature = "send", not(feature = "luau")))]
pub(crate) type HookCallback = Rc<dyn Fn(&Lua, Debug) -> Result<()> + Send>;

#[cfg(all(not(feature = "send"), not(feature = "luau")))]
pub(crate) type HookCallback = Rc<dyn Fn(&Lua, Debug) -> Result<()>>;

#[cfg(all(feature = "send", feature = "luau"))]
pub(crate) type InterruptCallback = Rc<dyn Fn(&Lua) -> Result<VmState> + Send>;

#[cfg(all(not(feature = "send"), feature = "luau"))]
pub(crate) type InterruptCallback = Rc<dyn Fn(&Lua) -> Result<VmState>>;

#[cfg(all(feature = "send", feature = "lua54"))]
pub(crate) type WarnCallback = Box<dyn Fn(&Lua, &str, bool) -> Result<()> + Send>;

#[cfg(all(not(feature = "send"), feature = "lua54"))]
pub(crate) type WarnCallback = Box<dyn Fn(&Lua, &str, bool) -> Result<()>>;

#[cfg(feature = "send")]
pub trait MaybeSend: Send {}
#[cfg(feature = "send")]
impl<T: Send> MaybeSend for T {}

#[cfg(not(feature = "send"))]
pub trait MaybeSend {}
#[cfg(not(feature = "send"))]
impl<T> MaybeSend for T {}

/// A Luau vector type.
///
/// By default vectors are 3-dimensional, but can be 4-dimensional
/// if the `luau-vector4` feature is enabled.
#[cfg(any(feature = "luau", doc))]
#[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
#[derive(Debug, Default, Clone, Copy, PartialEq)]
pub struct Vector(pub(crate) [f32; Self::SIZE]);

#[cfg(any(feature = "luau", doc))]
impl fmt::Display for Vector {
    #[rustfmt::skip]
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        #[cfg(not(feature = "luau-vector4"))]
        return write!(f, "vector({}, {}, {})", self.x(), self.y(), self.z());
        #[cfg(feature = "luau-vector4")]
        return write!(f, "vector({}, {}, {}, {})", self.x(), self.y(), self.z(), self.w());
    }
}

#[cfg(any(feature = "luau", doc))]
impl Vector {
    pub(crate) const SIZE: usize = if cfg!(feature = "luau-vector4") { 4 } else { 3 };

    /// Creates a new vector.
    #[cfg(not(feature = "luau-vector4"))]
    pub const fn new(x: f32, y: f32, z: f32) -> Self {
        Self([x, y, z])
    }

    /// Creates a new vector.
    #[cfg(feature = "luau-vector4")]
    pub const fn new(x: f32, y: f32, z: f32, w: f32) -> Self {
        Self([x, y, z, w])
    }

    /// Creates a new vector with all components set to `0.0`.
    #[doc(hidden)]
    pub const fn zero() -> Self {
        Self([0.0; Self::SIZE])
    }

    /// Returns 1st component of the vector.
    pub const fn x(&self) -> f32 {
        self.0[0]
    }

    /// Returns 2nd component of the vector.
    pub const fn y(&self) -> f32 {
        self.0[1]
    }

    /// Returns 3rd component of the vector.
    pub const fn z(&self) -> f32 {
        self.0[2]
    }

    /// Returns 4th component of the vector.
    #[cfg(any(feature = "luau-vector4", doc))]
    #[cfg_attr(docsrs, doc(cfg(feature = "luau-vector4")))]
    pub const fn w(&self) -> f32 {
        self.0[3]
    }
}

#[cfg(all(feature = "luau", feature = "serialize"))]
impl Serialize for Vector {
    fn serialize<S: Serializer>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error> {
        let mut ts = serializer.serialize_tuple_struct("Vector", Self::SIZE)?;
        ts.serialize_field(&self.x())?;
        ts.serialize_field(&self.y())?;
        ts.serialize_field(&self.z())?;
        #[cfg(feature = "luau-vector4")]
        ts.serialize_field(&self.w())?;
        ts.end()
    }
}

#[cfg(any(feature = "luau", doc))]
impl PartialEq<[f32; Self::SIZE]> for Vector {
    #[inline]
    fn eq(&self, other: &[f32; Self::SIZE]) -> bool {
        self.0 == *other
    }
}

pub(crate) struct DestructedUserdata;

/// An auto generated key into the Lua registry.
///
/// This is a handle to a value stored inside the Lua registry. It is not automatically
/// garbage collected on Drop, but it can be removed with [`Lua::remove_registry_value`],
/// and instances not manually removed can be garbage collected with
/// [`Lua::expire_registry_values`].
///
/// Be warned, If you place this into Lua via a [`UserData`] type or a rust callback, it is *very
/// easy* to accidentally cause reference cycles that the Lua garbage collector cannot resolve.
/// Instead of placing a [`RegistryKey`] into a [`UserData`] type, prefer instead to use
/// [`AnyUserData::set_user_value`] / [`AnyUserData::user_value`].
///
/// [`UserData`]: crate::UserData
/// [`RegistryKey`]: crate::RegistryKey
/// [`Lua::remove_registry_value`]: crate::Lua::remove_registry_value
/// [`Lua::expire_registry_values`]: crate::Lua::expire_registry_values
/// [`AnyUserData::set_user_value`]: crate::AnyUserData::set_user_value
/// [`AnyUserData::user_value`]: crate::AnyUserData::user_value
pub struct RegistryKey {
    pub(crate) registry_id: AtomicI32,
    pub(crate) unref_list: Arc<Mutex<Option<Vec<c_int>>>>,
}

impl fmt::Debug for RegistryKey {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "RegistryKey({})", self.id())
    }
}

impl Hash for RegistryKey {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.id().hash(state)
    }
}

impl PartialEq for RegistryKey {
    fn eq(&self, other: &RegistryKey) -> bool {
        self.id() == other.id() && Arc::ptr_eq(&self.unref_list, &other.unref_list)
    }
}

impl Eq for RegistryKey {}

impl Drop for RegistryKey {
    fn drop(&mut self) {
        let registry_id = self.id();
        // We don't need to collect nil slot
        if registry_id > ffi::LUA_REFNIL {
            let mut unref_list = self.unref_list.lock();
            if let Some(list) = unref_list.as_mut() {
                list.push(registry_id);
            }
        }
    }
}

impl RegistryKey {
    /// Creates a new instance of `RegistryKey`
    pub(crate) const fn new(id: c_int, unref_list: Arc<Mutex<Option<Vec<c_int>>>>) -> Self {
        RegistryKey {
            registry_id: AtomicI32::new(id),
            unref_list,
        }
    }

    /// Returns the underlying Lua reference of this `RegistryKey`
    #[inline(always)]
    pub fn id(&self) -> c_int {
        self.registry_id.load(Ordering::Relaxed)
    }

    /// Sets the unique Lua reference key of this `RegistryKey`
    #[inline(always)]
    pub(crate) fn set_id(&self, id: c_int) {
        self.registry_id.store(id, Ordering::Relaxed);
    }

    /// Destroys the `RegistryKey` without adding to the unref list
    pub(crate) fn take(self) -> i32 {
        let registry_id = self.id();
        unsafe {
            ptr::read(&self.unref_list);
            mem::forget(self);
        }
        registry_id
    }
}

pub(crate) struct ValueRef {
    pub(crate) lua: WeakLua,
    pub(crate) index: c_int,
    pub(crate) drop: bool,
}

impl ValueRef {
    #[inline]
    pub(crate) fn new(lua: &RawLua, index: c_int) -> Self {
        ValueRef {
            lua: lua.weak().clone(),
            index,
            drop: true,
        }
    }

    #[inline]
    pub(crate) fn to_pointer(&self) -> *const c_void {
        let lua = self.lua.lock();
        unsafe { ffi::lua_topointer(lua.ref_thread(), self.index) }
    }
}

impl fmt::Debug for ValueRef {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "Ref({:p})", self.to_pointer())
    }
}

impl Clone for ValueRef {
    fn clone(&self) -> Self {
        unsafe { self.lua.lock().clone_ref(self) }
    }
}

impl Drop for ValueRef {
    fn drop(&mut self) {
        if self.drop {
            if let Some(lua) = self.lua.try_lock() {
                unsafe { lua.drop_ref(self) };
            }
        }
    }
}

impl PartialEq for ValueRef {
    fn eq(&self, other: &Self) -> bool {
        assert!(
            self.lua == other.lua,
            "Lua instance passed Value created from a different main Lua state"
        );
        let lua = self.lua.lock();
        unsafe { ffi::lua_rawequal(lua.ref_thread(), self.index, other.index) == 1 }
    }
}

mod app_data;
mod sync;

#[cfg(test)]
mod assertions {
    use super::*;

    static_assertions::assert_impl_all!(RegistryKey: Send, Sync);

    #[cfg(not(feature = "send"))]
    static_assertions::assert_not_impl_any!(ValueRef: Send);
    #[cfg(feature = "send")]
    static_assertions::assert_impl_all!(ValueRef: Send, Sync);
}